Why Your Gutters Overflow and How to Fix It

Overflowing gutters are not just messy. Water that spills over the edge runs down the siding, soaks the soil by the foundation and can end up in the basement. Most overflows come from a handful of causes, and you can find out which one it is without climbing on anything.

Step 1: Watch it happen

1. Pick a rainy day, or run the hose on the roof edge safely from the ground, and watch where the water goes.
2. Note exactly where it overflows. Is it at one corner, along a whole run, or at a downspout?
3. Take photos, with the date. They help you compare later and are useful for a contractor.

Step 2: Check the common causes

A clogged gutter or downspout. This is the most likely culprit. If you can see leaves, or the water backs up, the gutter needs to be cleaned. See our guide to cleaning your gutters safely.

The slope is wrong. Gutters should tilt slightly toward the downspout, often about a quarter inch for every ten feet. Run water in the gutter and watch whether it flows toward the downspout or sits in a puddle. Water that pools may mean the gutter has sagged.

A missing or short downspout. Water that comes out right at the base of the wall soaks the foundation. This is the easiest fix.

Too much water for the gutter. Where two roof sections meet, a lot of water can pour into one spot and jump over the gutter. This is common at roof valleys.

Step 3: Extend the downspout

4. Attach a downspout extension to the bottom of each downspout so that water leaves at least four to six feet from the foundation.
5. Or use a splash block under the downspout to spread the water and direct it away.
6. Check the ground. The soil should slope away from the house, not toward it. If the water flows back, the grading may need work.

Step 4: Check the hardware from the ground

With binoculars, look along the gutter for:

• Gaps or sags where the gutter dips.
• Loose brackets or spikes pulling out of the fascia.
• Seams that drip.
• Stains on the siding below.

Do not climb up to fix these. A professional can re-hang and re-pitch gutters safely.

Step 5: Test your fix

After you have cleaned, extended or adjusted anything, test it rather than assuming it worked.

7. Run the hose at the high end of the gutter for a few minutes, at roughly the flow of a steady rain.
8. Watch the whole run from the ground. Water should move steadily toward the downspout, with no pooling, no spilling over the edge and no drips at the seams.
9. Check where the water lands. It should flow away from the house and keep going, not collect against the wall.
10. Test again in the next real rain, because a heavy downpour shows problems that a hose cannot.

Why this matters in a New England winter

Gutters that hold standing water in fall freeze in winter. The ice is heavy, and it can pull a gutter away from the house. Water that backs up at the roof edge can also freeze into an ice dam and force meltwater under the shingles. Fixing overflow before the first freeze is much cheaper than repairing what the ice does.

Common mistakes

• Cleaning only the gutter. Check the downspout too.
• Dumping water at the wall. Always extend it.
• Ignoring a sag. Water that pools freezes and pulls the gutter off in winter.
• Fixing a symptom. A rotted fascia needs repair first.

When it is more than overflow

Water that gets into the basement, rotten fascia or a gutter pulling away from the house are signs to call a professional. See the list below.